A ruler, a pen, a coin or any other known standard object placed alongside a pugmark or scat improves the ability to estimate the relative size of the photographed animal sign. This, in turn, allows an accurate identification of the species from the indirect evidence. For instance, without a clear understanding of size, it is sometime difficult to differentiate between the pugmark of a tiger and a leopard. However, a pen placed near the pugmark acts as a reference point for estimating size.

The width of this pugmark is greater than the length of a pen. An average pen measures about 14 centimeter or about 5.5 inch. We know from literature that the breadth of a leopard's pugmark never exceeds 9.5 centimeter. Thus, it is possible to conclude that this particular track belongs to a tiger.